A very crude Java shell.

This is a very basic interactive shell that allows one 
to create instances of classes and to manipulate these 
instances by calling methods. To simplify the parsing 
process an extremely simplified format is used for
input (which would be tedious in everyday use,
but the point of this exercise is not parsing,
but reflection):

 <variableName> <key> <parameter>*

the shell keeps a map that will associate
each variableName with the result of the operation.
Such variables will later be available as arguments
to other operations (actually, again to simplify
matters, this is the ONLY way to supply
arguments to operations).

<key> can be any of the primitives types ("int", "boolean", ...), 
"String", "new", "method", or "show".

"show" displays a variable's current value.

Primitives and "String" assign the appropriate value to a variable.

<variableName> new <Class> <parameter>*

instantiates <Class> using the appropriate constructor
for the supplied parameter values

<variableName> method <receiver> <methodName> <parameter>*

calls <receiver>.methodName(<parameter>*) and stores the return value
(or void) in <variableName>

An example interaction with the shell could be:

> java Shell
JAVA> a boolean true
a = Primitive boolean true
JAVA> c new java.lang.Frame
Exception while parsing and executing ...
java.lang.ClassNotFoundException: java.lang.Frame
        at java.net.URLClassLoader$1.run(URLClassLoader.java:199)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
        at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
        at java.lang.Class.forName0(Native Method)
        at java.lang.Class.forName(Class.java:141)
        at Shell.parseCommand(Shell.java:80)
        at Shell.main(Shell.java:151)
JAVA> c new java.awt.Frame
c = java.awt.Frame[frame0,0,0,0x0,invalid,hidden,layout=java.awt.BorderLayout,title=,resizable,normal]
JAVA> b int 300
b = Primitive int 300
JAVA> e method c resize b b
e = null
JAVA> e method c setVisible a
e = null
JAVA> d boolean false
d = Primitive boolean false
JAVA> e method c setVisible d
e = null
JAVA> c show
c = java.awt.Frame[frame0,0,0,300x300,hidden,layout=java.awt.BorderLayout,title=,resizable,normal]
JAVA> e method c setVisible a
e = null
JAVA> c show
c = java.awt.Frame[frame0,0,0,300x300,layout=java.awt.BorderLayout,title=,resizable,normal]